shot%# shot narrator · 2014. 7. 7. · shot%# shot narrator 1 algebraic*equations...
TRANSCRIPT
SHOT # SHOT NARRATOR
1 Algebraic equations represent the relationship
2 between quantities
3 using
4 letters to represent
5 unknown
6 quantities.
7 For example, Jason needs
8 to plan when to buy cat food.
9 Each of his four cats eats
10 half a cup of food each day,
11 or, two cups total.
12 This new bag of food holds forty-‐eight cups.
13 When he has
14 six cups left, he'll buy a new bag.
15 When will he need to buy more food?
16He can find the answer through simple subtraction-‐-‐
17 forty-‐eight cups minus two
18 each day
19 until six
20 cups remain.
21This method takes too much time! Is there is faster way?
22Yes-‐-‐he can write an algebraic equation in two simple steps.
23 The first step is to identify the variable-‐-‐
24 the number of days until six cups remain.
25The second step is to represent the variable with a suitable letter
26 like n for
27 number of days.
28 Two-‐n
29 represents the number of cups eaten. Here's why!
30 Since every
31 two cups eaten represents
32 one day, the number of cups eaten
33 can be found by multiplying
34
35 We want to know the value
36 of the unknown quantity in this relationship.
37 We know the bag has forty-‐eight cups of food
38and Jason wants to get more food when he has six cups left. The unknown quantity
39 can be represented by
40 2n,
41 creating this
42 equation.
43
44 Forty-‐eight minus six is
45 forty-‐two
46 which means 2n
47 is
48 forty-‐
49 two.
50Since two times n equals forty-‐two,two multiplied by
51 something must equal forty-‐two.
52 That "something" is twenty-‐one,
53 so n is twenty-‐one.
54 Jason knows
55 he needs
56 a new bag of cat food in twenty-‐one days
57 thanks to algebraic equations!